Hydrocarbon conversion with a multimetallic catalytic composite

ABSTRACT

Hydrocarbons are converted by contacting them at hydrocarbon conversion conditions with a trimetallic acidic catalytic composite comprising a combination of catalytically effective amounts of a platinum or palladium component, a rhodium component, a bismuth component, and a halogen component with a porous carrier material. The platinum or palladium component, rhodium component, and halogen component are present in the trimetallic catalyst in amounts respectively, calculated on an elemental basis, corresponding to about 0.01 to about 2 wt. % platinum or palladium, about 0.01 to about 2 wt. % rhodium, and about 0.1 to about 3.5 wt. % halogen. The bismuth component is present in amounts corresponding to an atomic ratio of bismuth to platinum or palladium of about 0.1:1 to about 1:1. Moreover, these metallic components are uniformly dispersed throughout the porous carrier material in carefully controlled oxidation states such that substantially all of the platinum or palladium, rhodium, and bismuth components are present therein in the corresponding elemental metallic states. A specific example of the type of hydrocarbon conversion process disclosed is a process for the catalytic reforming of a low-octane gasoline fraction wherein the gasoline fraction and hydrogen stream are contacted with the acidic trimetallic catalyst disclosed herein at reforming conditions.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of my prior, copendingapplication Ser. No. 436,305 filed Jan. 24, 1974, which in turn iscontinuation-in-part of my prior application Ser. No. 233,819 filed Mar.10, 1972, and now U.S. Pat. No. 3,798,155. All of the teachings of theseprior applications are specifically incorporated here by reference.

The subject of the present invention is a novel acidic trimetalliccatalytic composite which has exceptional activity, selectivity, andresistance to deactivation when employed in a hydrocarbon conversionprocess that required a catalyst having both ahydrogenation-dehydrogenation function and a selective acid or crackingfunction. More precisely, the present invention involves a noveldual-function acidic trimetallic catalytic composite which beneficiallyutilizes a catalytic component, bismuth, which traditionally has beenthought of and taught to be a poison for a platinum group metal becauseof its close proximity in the Periodic Table to the notorious platinumpoison, arsenic. Bismuth is utilized in the present invention tointeract with a platinum or palladium- and rhodium-containing acidiccatalyst to enable substantial improvements in hydrocarbon conversionprocesses of the type that have traditionally utilized platinum groupmetal-containing catalysts to accelerate the various hydrocarbonconversion reactions associated therewith. In another aspect, thisinvention concerns the improved processes that are produced by the useof an acidic trimetallic catalytic composite comprising a combination ofa platinum or palladium component, a rhodium component, a bismuthcomponent, and a halogen component with a porous, high surface areacarrier material in a manner such that (1) the platinum or palladium,bismuth, and rhodium components are uniformly dispersed throughout theporous carrier material, (2) the amount of the bismuth component is notgreater than the amount of the platinum or palladium component on anatomic basis and (3) substantially all of the platinum or palladium,rhodium, and bismuth components are present therein as the correspondingelemental metals. In a specific aspect, the present invention concernsan improved reforming process which utilizes the subject acidictrimetallic catalyst to markedly improve activity, selectivity, andstability characteristics associated therewith, to increase yields ofC₅ + reformate and of hydrogen recovered therefrom and to allowoperation thereof at high severity conditions not heretofore generallyemployed in the art of continuous catalytic reforming of hydrocarbonswith a platinum-containing monometallic, dual-function catalyst.

Composites having a hydrogenation-dehydrogenation function and aselective acid or cracking function are widely used today as catalystsin many industries, such as the petroleum or petrochemical industry, toaccelerate a wide spectrum of hydrocarbon conversion reactions.Generally, the cracking function is thought to be associated with anacid-acting material of the porous, adsorptive, refractory oxide typewhich is typically utilized as the support or carrier for a heavymetallic component such as the metals or compounds of metals of thetransition elements of Groups V through VIII of the Periodic Table towhich are generally attributed the hydrogenation-dehydrogenationfunction.

These catalytic composites are used to accelerate a wide variety ofhydrocarbon conversion reactions such as hydrocracking, isomerization,dehydrogenation, hydrogenation, desulfurization, cyclization,alkylation, polymerization, halogenation, hydrogenolysis, cracking,hydroisomerization, etc. In many cases, the commercial applications ofthese catalysts are in processes where more than one of these reactionsare proceeding simultaneously. An example of this type of process isreforming wherein a hydrocarbon feed stream containing paraffins andnaphthenes is subjected to conditions which promote dehydrogenation ofnaphthenes to aromatics, dehydrocyclization of paraffins to aromatics,isomerization of paraffins and naphthenes, hydrocracking of naphthenesand paraffins, and the like reactions to produce an octane-rich oraromatic-rich product stream. Another example is a hydrocracking processwherein catalysts of this type are utilized to effect selectivehydrogenation and cracking of high molecular weight unsaturatedmaterials, selective hydrocracking of high molecular weight materials,and other like reactions, to produce a generally lower boiling, morevaluable output stream. Yet another example is a hydroisomerizationprocess wherein a hydrocarbon fraction which is relatively rich instraight-chain paraffin and/or olefinic compounds are contacted with adual-function catalyst to produce an output stream rich in isoparaffincompounds.

Regardless of the reaction involved or the particular process involved,it is of critical importance that the dual-function catalyst exhibit notonly the capability to initially perform its specified functions butalso that it has the capability to perform them satisfactorily forprolonged periods of time. The analytical terms used in the art tomeasure how well a particular catalyst performs its intended functionsin a particular hydrocarbon conversion environment are activity,selectivity, and stability. And for purposes of discussion here theseterms are conveniently defined for a given charge stock as follows: (1)activity is a measure of the catalyst's ability to convert hydrocarbonreactants into products at a specified severity level where severitylevel means the reaction conditions used--that is, the temperature,pressure, contact time, and presence of diluents such as H₂ ; (2)selectivity refers to the amount of desired product or products obtainedrelative to the amount of reactants converted or charged; (3) stabilityrefers to the rate of change with time of the activity and selectivityparameters--obviously, the smaller rate implying the more stablecatalyst. In a reforming process, for example, activity commonly refersto the amount of conversion that takes place for a given charge stock ata specified severity level and is typically measured by octane number ofthe C₅ + product stream; selectivity usually refers to the amount ofC₅ + yield that is obtained at the particular severity or activity levelrelative to the amount of the charge stock; and stability is typicallyequated to the rate of change with time of activity, as measured byoctane number of C₅ + product and of selectivity, as measured by C₅ +yield. Actually, this last statement is not strictly correct becausegenerally a continuous reforming process is run to produce a constantoctane C₅ + product with a severity level being continuously adjusted toattain this result; and, furthermore, the severity level is for thisprocess usually varied by adjusting the conversion temperature in thereaction zone so that, in point of fact, the rate of change of activityfinds response to the rate of change of conversion temperatures andchanges in this last parameter are customarily taken as indicative ofactivity stability.

As is well known to those skilled in the art, the principal cause ofobserved deactivation or instability of a dual-function catalyst when itis used in a hydrocarbon conversion reaction is associated with the factthat coke forms on the surface of the catalyst during the carse of thereaction. More specifically, in these hydrocarbon conversion processes,the conditions utilized typically result in the formation of heavy, highmolecular weight, black, solid or semi-solid, carbonaceous materialwhich is a hydrogen-deficient polymeric substance having properties akinto both polynuclear aromatics and graphite. This material coats thesurface of the catalyst and reduces its activity by shielding its activesites from the reactants. In other words, the performance of thisdual-function catalyst is sensitive to the presence of carbonaceousdeposits on the surface of the catalyst. Accordingly, the major problemfacing workers in this area of the art is the development of more activeand selective catalytic composites that are not as sensitive to thepresence of these carbonaceous materials and/or have the capability tosuppress the rate of formation of these carbonaceous material on thecatalyst. Viewed in terms of performance parameters, the problem is todevelop a dual-function catalyst having superior activity, selectivity,and stability. In particular, for a reforming process the problem istypically expressed in terms of shifting and stabilizing the C₅ +yield-octane relationship--C₅ + yield being representative ofselectivity and octane being proportional to activity.

I have now found a dual-function catalytic composite which possessesimproved activity, selectivity, and stability when it is employed in aprocess for the conversion of hydrocarbons of the type which haveheretofore utilized dual-function catalytic composites such as processesfor isomerization, hydroisomerization, dehydrogenation, desulfurization,denitrogenization, hydrogenation, alkylation, dealkylation,disproportionation, polymerization, oligomerization, hydrodealkylation,transalkylation, cyclization, dehydrocyclization, hydrogenolysis,cracking, hydrocracking, reforming, hydrogenation, halogenation, and thelike processes. In particular, I have ascertained that an acidictrimetallic catalytic composite, comprising a combination of a platinumor palladium component, a bismuth component, a rhodium component, and ahalogen component with a porous refractory carrier material can enablethe performance of a hydrocarbon conversion process utilizing adual-function catalyst to be substantially improved, provided theamounts and oxidation states of the metallic components and thedistribution thereof in the catalytic composite are carefully controlledin the manner indicated herein. Since the earliest introduction ofcatalysts containing a platinum group component, it has been axiomaticthat the effect of arsenic on a platinum-containing catalyst isdetrimental. This concept has become so fixed and certain in the artthat tremendous efforts have been devoted to removing arseniccontaminants from charge stocks that are to be processed in a unitcontaining a platinum catalyst. In addition, the art is replete with asignificant number of methods for reactivating a platinum-containingcatalyst once it has been deactivated by contact with arsenic orcompounds of arsenic. Because bismuth is a member of the same group ofthe Periodic Table (Group VA) and is known to have similar chemicalproperties to arsenic, it has fallen into the same category and has beentraditionally thought of as a poison for a platinum-containing catalyst.The art has on occassion hinted at or proposed to use the poisoningeffect of Group VA metallic elements to modify or attenuate the platinumcomponent of a dual-function catalyst. For examples of thesesuggestions, reference may be had to the teachings of U.S. Pat. Nos.3,156,737; 3,206,391; 3,291,755, and 3,511,888. However, the art has notrecognized that bismuth can be utilized to promote a platinum-containingcatalyst; that is, to simultaneously increase its activity, selectivity,and stability in hydrocarbon conversion service. In particular, the arthas apparently never contemplated the use of a platinum-bismuth catalystin a catalytic reforming process. As a matter of fact, the art on thislast process is replete with teachings that contact of theplatinum-containing reforming catalyst, with metallic elements of GroupVA of the Periodic Table, and particularly arsenic, is to be avoided ifat all possible, and if contact occurs to any substantial degree, thecatalyst must be immediately regenerated or reactivated by proceduresfor removal of these detrimental Group VA constituents. In sharpcontrast to this historic teaching of the art that bismuth isdetrimental to a platinum-containing reforming catalyst, I have nowdiscerned that the presence of bismuth in a catalyst containing aplatinum or palladium component and a rhodium component can be verybeneficial under certain conditions. One essential condition associatedwith the acquisition of the beneficial aspects of bismuth with this typeof platinum- or palladium-containing catalyst is the atomic ratio ofbismuth to platinum or palladium contained in the composite; my findingshere indicate that it is only when this ratio is not greater than 1:1that the beneficial interaction of bismuth with the platinum- orpalladium metal and the rhodium metal is obtained. A second condition isthe presence of a halogen component; my finding on this matter is thatthe presence of a relatively small amount of halogen is required to seethe beneficial effect. Another condition for achieving this beneficialinteraction of bismuth with this type of catalyst is the distribution ofthe bismuth, rhodium, and platinum or palladium components in thecarrier material with which they are combined; my finding here is thatit is essential that these components be uniformly dispersed throughoutthe porous carrier material--that is, the concentration of thesecomponents is approximately the same in any reasonably divisible portionthereof. Still another condition for this beneficial effect is theoxidation states of the metallic components; my finding here is that itis essential that the bismuth, rhodium, and platinum or palladiumcomponents are present in the composite in the corresponding elementalmetallic states. A trimetallic acidic catalyst meeting these essentiallimitations differs sharply, both in substance and in capabilities fromthe bismuth- and platinum-containing catalyst that are suggested by theprior art.

In the case of a reforming process, one of the principal advantagesassociated with the use of the instant acidic trimetallic catalystinvolves the acquisition of the capability to operate in a stable mannerin a high severity operation; for example, a continuous reformingprocess producing a C₅ + reformate having an octane of about 100 F-1clear and utilizing a relatively low pressure of 50 to about 350 psig.In this latter embodiment the principal effect of the bismuth componentis to stabilize the platinum or palladium component and the rhodiumcomponent by providing a mechanism for allowing them to better resistthe rather severe deactivation normally associated with theseconditions. In short, the present inveniton essentially involves thefinding that the addition of a controlled amount of a bismuth componentto a dual-function hydrocarbon conversion catalyst, containing aplatinum or palladium component, a rhodium component, and a halogencomponent, coupled with the uniform distribution of the bismuthcomponent throughout the catalytic composite to achieve an atomic ratioof bismuth to platinum or palladium metal of not greater than 1:1 andwith careful control of the oxidation states of the metallic componentsenables the performance characteristics of the catalyst to be sharplyand materially improved.

It is, accordingly, one object of the present invention to provide anacidic trimetallic hydrocarbon conversion catalyst having superiorperformance characteristics when utilized in a hydrocarbon conversionprocess. A second object is to provide an acidic trimetallic catalysthaving dual-function hydrocarbon conversion performance characteristicsthat are relatively insensitive to the deposition of hydrocarbonaceousmaterial thereon. A third object is to provide preferred methods ofpreparation of this trimetallic catalytic composite which insures theachievement and maintenance of its beneficial properties. Another objectis to provide an improved reforming catalyst having superior activity,selectivity, and stability when employed in a low pressure reformingprocess. Yet another object is to provide a dual-function hydrocarbonconversion catalyst which utilizes a relatively inexpensive component,bismuth, to promote and stabilize a platinum or palladium component anda rhodium component. Still another object is to provide a method ofpreparation of a bismuth-containing trimetallic catalyst which insuresthe bismuth component is in a highly dispersed metallic state during usein the conversion of hydrocarbons.

In brief summary, the present invention is, in one embodiment, acatalytic composite comprising a porous carrier material containing, onan elemental basis, about 0.01 to about 2 wt. % platinum or palladium,about 0.1 to about 3.5 wt. % halogen, about 0.01 to about 2 wt. %rhodium, and bismuth in an amount sufficient to result in an atomicratio of bismuth to platinum or palladium of about 0.1:1 to about 1:1,wherein the platinum or palladium, bismuth, and rhodium are uniformlydispersed throughout the porous carrier material, and whereinsubstantially all of the platinum or palladium, rhodium, and bismuth arepresent in the corresponding elemental metallic states.

A second embodiment relates to a catalytic composite comprising a porouscarrier material containing, on an elemental basis, about 0.05 to about1 wt. % platinum, about 0.5 to about 1.5 wt. % halogen, about 0.05 toabout 1 wt. % rhodium, and bismuth in an amount sufficient to result inan atomic ratio of bismuth to platinum of about 0.1:1 to about 0.75:1,wherein substantially all of the platinum, rhodium, and bismuth arepresent in the corresponding elemental metallic states, and wherein themetallic ingredients are uniformly dispersed in the porous carriermaterial.

Another embodiment relates to a catalytic composite comprising acombination of the catalytic composite described in the first or secondembodiment with a sulfur component in an amount sufficient toincorporate about 0.01 to about 0.5 wt. % sulfur, calculated on anelemental basis.

Yet another embodiment relates to a process for the conversion ofhydrocarbons comprising contacting the hydrocarbon and hydrogen with thecatalytic composite described above in the first or second embodimentsat hydrocarbon conversion conditions.

A preferred embodiment relates to a process for reforming a gasolinefraction which comprises contacting the gasoline fraction and hydrogenwith the catalytic composite described above in the first or secondembodiments at reforming conditions selected to produce a high-octanereformate.

Other objects and embodiments of the present invention relate toadditional details regarding preferred catalytic ingredients, preferredamounts of ingredients, suitable methods of composite preparation,operating conditions for use in the hydrocarbon conversion processes,and the like particulars which are hereinafter given in the followingdetailed discussion of each of these facets of the present invention.

The acidic trimetallic catalyst of the present invention comprises aporous carrier material or support having combined therewithcatalytically effective amounts of a platinum or palladium component, abismuth component, a rhodium component, and a halogen component.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the hydrocarbon conversion process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts such as: (1) activated carbon, coke, orcharcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically-prepared andnaturally-occurring, which may or may not be acid treated, for example,attapulgus clay, china clay, diatomaceous earth, fuller's earth,kaoline, kieselguhr, etc.; (3) ceramics, porcelain, crushed firebrick,bauxite; (4) refractory inorganic oxides such as alumina, titaniumdioxide, zirconium dioxide, chromium oxide, beryllium oxide, vanadiumoxide, cerium oxide, hafnium oxide, zinc oxide, magnesia, thoria, boria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc; (5) zeolitic crystalline aluminosilicates such asnaturally-occurring or synthetically-prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, CaAl₂ O₄, and other like compounds having the formulaMO.Al₂ O₃ where M is a metal having a valence of 2; and (7) combinationsof elements from one or more of these groups. The preferred porouscarrier materials for use in the present invention are refractoryinorganic oxides, with best results obtained with a carrier materialconsisting essentially of alumina. Suitalbe alumina materials are thecrystalline aluminas known as the gamma-, eta-, and theta-alumina, withgamma- or eta-alumina giving best results. In addition, in someembodiments, the alumina carrier material may contain minor proportionsof other well known refractory inorganic oxides such as silica-zirconia,magnesia, etc.; however, the preferred support is substantially puregamma- or eta-alumina. Preferred carrier materials have an apparent bulkdensity of about 0.3 to about 0.9 g/cc and surface area characteristicssuch that the average pore diameter is about 20 to 300 Angstroms, thepore volume is about 0.1 to about 1 cc/g and the surface area is about100 to about 500 m² /g. In general, best results are typically obtainedwith a gamma-alumina carrier material which is used in the form ofspherical particles having: a relatively small diameter (i.e. typicallyabout 1/16 inch), an apparent bulk denstiy of about 0.3 to about 0.8g/cc, a pore volume of about 0.4 cc/g, and a surface area of about 175m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically-prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc.; in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere; and alumina spheres may becontinuously manufactured by the well known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resulting hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. This treatment effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

One essential ingredient of the present catalytic composite is a rhodiumcomponent. It is of fundamental importance that substantially all of therhodium component exists within the catalytic composite of the presentinvention in the elemental metallic state and the subsequently describedreduction procedure is designed to accomplish this objective. Therhodium component may be utilized in the composite in any amount whichis catalytically effective, with the preferred amount being about 0.01to about 2 wt. % thereof, calculated on an elemental basis. Typically,best results are obtained with about 0.05 to about 1 wt. % rhodium. Itis additionally preferred to select the specified amount of rhodium fromwithin this broad weight range as a function of the amount of theplatinum or palladium component, on an atomic basis, as is explainedhereinafter.

This rhodium component may be incorporated into the catalytic compositein any suitable manner known to those skilled in the catalystformulation art which results in a relatively uniform distribution ofrhodium in the carrier material. In addition, it may be added at anystage of the preparation of the composite--either during preparation ofthe carrier material or thereafter--and the precise method ofincorporation used is not deemed to be critical. However, best resultsare obtained when the rhodium component is relatively uniformlydistributed throughout the carrier material, and the preferredprocedures are the ones known to result in a composite having thisrelatively uniform distribution. One acceptable procedure forincorporating this component into the composite involves cogelling orcoprecipitating the rhodium component during the preparation of thepreferred carrier material, alumina. This procedure usually comprehendsthe addition of a soluble, decomposable compound of rhodium such asrhodium trichloride hydrate to the alumina hydrosol before it is gelled.The resulting mixture is then finished by conventional gelling, aging,drying, and calcination steps as explained hereinbefore. A preferred wayof incorporating this component is an impregnation step wherein theporous carrier material is impregnated with a suitablerhodium-containing solution either before, during, or after the carriermaterial is calcined. Preferred impregnation solutions are aqueoussolutions of water soluble, decomposable rhodium compounds such ashexammine rhodium chloride, rhodium carbonylchloride, rhodiumtrichloride hydrate, rhodium nitrate, sodium hexachloromodate (III),sodium hexanitrorhodate (III), rhodium sulfate, and the like compounds.Best results are ordinarily obtained when the impregnation solution isan aqueous solution of rhodium trichloride hydrate or rhodium nitrate.This component can be added to the carrier material either prior to,simultaneously with, or after the other metallic components are combinedtherewith. Best results are usually achieved when this component isadded simultaneously with the other metallic components. In fact,excellent results are obtained, as reported in the examples, with a onestep impregnation procedure using an aqueous solution comprisingchloroplatinic or chloropalladic acid, rhodium trichloride hydrate,hydrochloric acid, and bismuth trichloride.

A second essential ingredient of the subject catalyst is the platinum orpalladium component. That is, it is intended to cover the use ofplatinum or palladium or mixtures thereof as a second component of thepresent composite. It is an essential feature of the present inventionthat substantially all of the platinum or palladium component existswithin the final catalytic composite in the elemental metallic state(i.e., as elemental platinum or palladium). Generally, the amount of thesecond component used in the final composite is relatively smallcompared to the amount of the other components combined therewith. Infact, the platinum or palladium component generally will comprise about0.01 to about 2 wt. % of the final catalytic composite, calculated on anelemental basis. Excellent results are obtained when the catalystcontains about 0.05 to about 1 wt. % or platinum or palladium metal.

This platinum or palladium component may be incorporated in thecatalytic composite in any suitable manner known to result in arelatively uniform distribution of this component in the carriermaterial such as coprecipitation or cogellation, ion-exchange, orimpregnation. The preferred method of preparing the catalyst involvesthe utilization of a soluble, decomposable compound of platinum orpalladium to impregnate the carrier material in a relatively uniformmanner. For example, this component may be added to the support bycommingling the latter with an aqueous solution of chloroplatinic orchloropalladic acid. Other water-soluble compounds of platinum orpalladium may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II),tetrammine-platinum (II) chloride, palladium chloride, palladiumnitrate, palladium sulfate, diammine-palladium (II), hydroxide,tetrammine-palladium (II) chloride, etc. The utilization of a platinumor palladium chloride compound, such as chloroplatinic or chloropalladicacid, is preferred since it facilitates the incorporation of both theplatinum or palladium component and at least a minor quantity of thehalogen component in a single step. Hydrogen chloride or the like acidis also generally added to the impregnation solution in order to furtherfacilitate the incorporation of the halogen component and the uniformdistribution of the metallic component throughout the carrier material.In addition, it is generally preferred to impregnate the carriermaterial after it has been calcined in order to minimize the risk ofwashing away the valuable platinum or palladium compounds; however, insome cases it may be advantageous to impregnate the carrier materialwhen it is in a gelled state.

Yet another essential constituent of the trimetallic composite of thepresent invention is a bismuth component. It is an essential feature ofthe present invention that substantially all of this component ispresent in the composite as the elemental metal. That is, it is believedto be a prerequisite for the acquisition of the beneficial effect ofbismuth on a platinum-containing catalyst that the bismuth componentexists in the catalytic composite in the zero oxidation state. All ofthe methods of preparation of the catalytic composite of the presentinvention include a substantially water-free prereduction step which isdesigned to result in the composite containing substantially all of thebismuth component in the elemental metallic state.

The bismuth component may be incorporated into the catalytic compositein any suitable manner known to effectively disperse this componentthroughout the carrier material or to result in this conditions. Thus,this incorporation may be accomplished by coprecipitation or cogellationwith the porous carrier material, ion-exchange with the carrier materialwhile it is in a gel state, or impregnation of the carrier material atany stage in its preparation. It is to be noted that it is intended toinclude within the scope of the present invention all conventionalmethods for incorporating a metallic component in a catalytic compositewhich results in a uniform distribution of the metllic componentthroughout the associated carrier material. One preferred method ofincorporating the bismuth component into the catalytic compositeinvolves coprecipitating the bismuth component during the preparation ofthe preferred refractory oxide carrier material. Typically, thisinvolves the addition of a suitable, soluble, decomposable bismuthcompound or complex to the alumina hydrosol, and then combining thehydrosol with a suitable gelling agent and dropping the resultingmixture into an oil bath as explained in detail hereinbefore. Afterdrying and calcining the resulting gelled carrier material, there isobtained an intimate combination of alumina and bismuth oxide, whichcombination has the bismuth component uniformly dispersed throughout thealumina. Another preferred method of incorporating the bismuth componentinto the catalytic composite involves the utilization of a solubledecomposable compound or complex of bismuth to impregnate the porouscarrier material. In general, the solvent used in this preferredimpregnation step is selected on the basis of its capability to dissolvethe desired bismuth compound and is typically an aqueous acidicsolution. Hence, the bismuth component may be added to the carriermaterial by commingling the latter with an aqueous solution of asuitable bismuth salt or water-soluble compound or complex of bismuthsuch as bismuth ammonium citrate, bismuth tribromide, bismuthtrichloride, bismuth trihydroxide, bismuth oxybromide, bismuthoxychloride, bismuth trioxide, bismuth potassium tartrate, bismuthacetate, bismuth oxycarbonate, bismuth nitrate, and the like compounds.Best results are ordinarily obtained with a solution of bismuthtrichloride in hydrochloric acid. In general, the bismuth component canbe impregnated either prior to, simultaneously with, or after the othermetallic components are added to the carrier material. However, I haveobtained excellent results by impregnating the bismuth componentsimultaneously with the platinum or palladium and rhodium components. Infact, I have determined that a preferred impregnation solution containschloroplatinic acid, rhodium trichloride hydrate, hydrochloric acid, andbismuth trichloride.

Regardless of which bismuth compound is used in the preferredimpregnation step, it is important that the bismuth component beuniformly distributed throughout the carrier material. In order toachieve this objective it is necessary to maintain the pH of theimpregnation solution at a value less than 3, and preferably less than1, and to dilute the solution to a volume which is approximately thesame or greater than the volume of the carrier material which isimpregnated. It is preferred to use a volume ratio of impregnationsolution to void volume of carrier material of at least 0.75:1 andpreferably about 1:1 to about 3:1 or more. Similarly, a relatively longcontact time should be used during this impregnation step ranging fromabout 0.25 hours up to about 0.5 hours or more. The carrier material islikewise preferably constantly agitated during this impregnation step.

It is essential to incorporate a halogen component into the trimetalliccatalytic composite of the present invention. Although the precise formof the chemistry of the association of the halogen component with thecarrier material is not entirely known, it is customary in the art torefer to the halogen component as being combined with the carriermaterial, or with the other indredients of the catalyst in the form ofthe halide (e.g., as the combined chloride). This combined halogen maybe either fluorine, chlorine, bromine, or mixtures thereof. Of thesefluorine and, particularly, chlorine are preferred for the purpose ofthe present invention. The halogen may be added to the carrier materialin any suitable manner, either during preparation of the support orbefore or after the addition of the other components. For example, thehalogen may be added, at any stage of the preparation of the carriermaterial or to the calcined carrier material, as an aqueous solution ofa suitable, decomposable halogen-containing compound such as hydrogenfluoride, hydrogen chloride, hydrogen bromide, ammonium chloride, etc.The halogen component or a portion thereof, may be combined with thecarrier material during the impregnation of the latter with the metalliccomponents; for example, through the utilization of a mixture ofchloroplatinic acid, bismuth trichloride, and hydrogen chloride. Inanother situation, the alumina hydrosol which is typically utilized toform the preferred alumina carrier material may contain halogen and thuscontribute at least a portion of the halogen component to the finalcomposite. For reforming, the halogen will be typically combined withthe carrier material in an amount sufficient to result in a finalcomposite that contains about 0.1 to about 3.5% and preferably about 0.5to about 1.5 % by weight of halogen, calculated on an elemental basis.In isomerization or hydrocracking embodiments, it is generally preferredto utilize relatively larger amounts of halogen in thecatalyst--typically, ranging up to about 10 wt. % halogen, calculated onan elemental basis, and more preferably, about 1 to about 5 wt. %. It isto be understood that the specified level of halogen component in theinstant catalyst can be achieved or maintained during use in theconversion of hydrocarbons by continuously or periodically adding to thereaction zone a decomposable halogen-containing compound such as anorganic chloride (e.g., ethylene dichloride, carbon tetrachloride,t-butyl chloride) in an amount of about 1 to 100 wt. ppm. of thehydrocarbon feed, and preferably about 1 to 10 wt. ppm.

Regarding the preferred amounts of the various metallic components ofthe subject catalyst, I have found it to be a preferred practice toselect the amount of the rhodium component to produce a compositecontaining an atomic ratio of rhodium to platinum or palladium withinthe broad range of about 0.1:1 to about 2:1, with the preferred rangebeing about 0.25:1 to about 1.5:1. Similarly, I have found that it isessential to fix the amount of the bismuth component as a function ofthe amount of the platinum or palladium component contained in thecomposite. More specifically, I have observed that the beneficialinteraction of the bismuth component with the platinum or palladiumcomponent is only obtained when the bismuth component is present, on anatomic basis, in an amount not greater than the platinum or palladiumcomponent. Quantitatively, the amount of the bismuth component ispreferably sufficient to provide an atomic ratio of bismuth to platinumor palladium of about 0.1:1 to about 1:1, with best results obtained atan atomic ratio of about 0.1:1 to about 0.75:1. The criticalnessassociated with this atomic ratio limitation is apparent when an attemptis made to convert hydrocarbons with a catalyst having an atomic ratioof bismuth to platinum or palladium metal of greater than 1:1. In thislatter case substantial deactivation of the platinum or palladiumcomponent is observed. Accordingly, it is an essential feature of thepresent invention that the amount of the bismuth component is chosen asa function of the amount of the platinum or palladium component in orderto insure that the atomic ratio of these components in the resultingcatalyst is within the stated range. Specific examples of especiallypreferred catalytic composites are as follows: (1) a catalytic compositecomprising 0.375 wt. % platinum, 0.375 wt. % rhodium, 0.25 wt. %bismuth, and 0.5 to 1.5 wt. % halogen combined with an alumina carriermaterial (atomic ratio Bi to Pt = 0.622:1); (2) a catalytic compositecomprising 0.375 wt. % platinum, 0.375 wt. % rhodium, 0.15 wt. %bismuth, and 0.5 to 1.5 wt. % halogen combined with an alumina carriermaterial (atomic ratio Bi to Pt = 0.38:1); (3) a catalytic compositecomprising 0.375 wt. % platinum, 0.2 wt. % rhodium, 0.1 wt. % bismuth,and 0.5 to 1.5 wt. % halogen combined with an alumina carrier material(atomic ratio Bi to Pt = 0.25:1); (4) a catalytic composite comprising0.375 wt. % platinum, 0.375 wt. % rhodium, 0.5 wt. % bismuth, and 0.5 to1.5 wt. % halogen combined with an alumina carrier material (atomicratio Bi to Pt = 0.126:1); and, (5) a catalytic composite comprising0.75 wt. % platinum, 0.1 wt. % rhodium, 0.4 wt. % bismuth, and 0.5 to1.5 wt. % halogen combined with an alumina carrier material (atomicratio Bi to Pt = 0.5:1).

Another significant parameter for the present catalyst is the "totalmetals content" which is defined to be the sum of the platinum orpalladium component, the bismuth component, and the rhodium component,calculated on an elemental basis. Good results are ordinarily obtainedwith the subject catalyst when this parameter is fixed at a value ofabout 0.15 to about 2.5 wt. %, with best results ordinarily achieved ata metals loading of about 0.3 to about 2 wt. %.

An optional ingredient for the trimetallic catalyst of the presentinvention is a Friedel-Crafts metal halide component. This ingredient isparticularly useful in hydrocarbon conversion embodiments of the presentinvention, wherein it is preferred that the catalyst utilized has astrong acid or cracking function associated therewith--for example, anembodiment wherein hydrocarbons are to be hydrocracked or isomerizedwith the catalyst of the present invention. Suitable metal halides ofthe Friedel-Crafts type include aluminum chloride, aluminum bromide,ferric chloride, ferric bromide, zinc chloride, and the like compounds,with the aluminum halides and particularly aluminum chloride ordinarilyyielding best results. Generally, this optional ingredient can beincorporated into the composite of the present invention by any of theconventional methods for adding metallic halides of this type; however,best results are ordinarily obtained when the metallic halide issublimed onto the surface of the carrier material according to thepreferred method disclosed in U.S. Pat. No. 2,999,074. The component cangenerally be utilized in any amount which is catalytically effective,with a value selected from the range of about 1 to about 100 wt. % ofthe carrier material generally being preferred.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the final catalyst generallywill be dried at a temperature of about 200° to about 600° F. for aperiod of at least about 2 to 24 hours or more, and finally calcined oroxidized at a temperature of about 700° F. to about 1100° F. in an airor oxygen atmosphere for a period of about 0.5 to about 10 hours inorder to convert substantially all of the metallic components to thecorresponding oxide forms. Because a halogen component is utilized inthe catalyst, best results are generally obtained when the halogencontent of the catalyst is adjusted during the calcination step byincluding a halogen, hydrogen halide, or a halogen-containing compoundin the air atmosphere utilized. In particular, when the halogencomponent of the catalyst is combined chloride, it is preferred to use amole ratio of H₂ O to HCl of about 5:1 to about 100:1 during at least aportion of the calcination step in order to adjust the final chlorinecontent of the catalyst to a range of about 0.1 to about 3.5 wt. %.

It is an essential feature of the present invention that the resultantoxidized trimetallic catalytic composite is subjected to a substantiallywater-free reduction step prior to its use in the conversion ofhydrocarbons. This step is designed to insure a uniform and finelydivided dispersion of the metallic components throughout the carriermaterial and to selectively reduce substantially all of the platinum orpalladium component, the rhodium component, and the bismuth component tothe corresponding metals. Preferably, substantially pure and dryhydrogen (i.e., less than 20 vol. ppm. H₂ O) is used as the reducingagent in this step. The reducing agent is contacted with the oxidizedcatalyst at conditions including a temperature of about 800° F. to about1200° F., a gas hourly space velocity of about 100 to about 5000hr..sup.⁻¹, and a period of time of about 0.5 to 10 hours effective toreduce substantially all of the platinum or palladium, rhodium, andbismuth components to the corresponding elemental metallic states. Thisreduction treatment may be performed in situ as part of a startupsequence if precautions are taken to predry the plant to a substantiallywater-free state and if substantially water-free hydrogen is used.

The resulting reduced catalytic composite may, in some cases, bebeneficially subjected to a presulfiding operation designed toincorporate in the catalytic composite from about 0.01 to about 0.5 wt.% sulfur, calculated on an elemental basis, in the form of the adsorbedsulfide. Preferably, this presulfiding treatment takes place in thepresence of hydrogen and a sulfiding reagent which is a suitablesulfur-containing and metallic sulfide-producing compound such ashydrogen sulfide, lower molecular weight mercaptans, organic sulfide,disulfides, etc. Typically, this procedure comprises treating theselectively reduced catalyst with a sulfiding gas such as a mixture ofhydrogen and hydrogen sulfide having about 10 moles of hydrogen per moleof hydrogen sulfide at conditions sufficient to effect the desiredincorporation of sulfur, generally including a temperature ranging fromabout 50° F. up to about 1100° F. or more. It is generally a goodpractice to perform this presulfiding step under substantiallywater-free conditions.

According to the present invention, a hydrocarbon charge stock andhydrogen are contacted with the previously characterized trimetalliccatalyst in a hydrocarbon conversion zone. This contacting may beaccomplished by using the catalyst in a fixed bed system, a moving bedsystem, a fluidized bed system, or in a batch type operation; however,in view of the danger of attrition losses of the valuable catalyst, andof well known operational advantages, it is preferred to use a fixed bedsystem. In this system, a hydrogen-rich gas and the charge stock arepreheated by any suitable heating means to the desired reactiontemperature and then are passed into a conversion zone containing afixed bed of the catalyst type previously characterized. It is, ofcourse, understood that the conversion zone may be one or more separatereactors with suitable means therebetween to insure that the desiredconversion temperature is maintained at the entrance to each reactor. Itis also important to note that the reactants may be contacted with thecatalyst bed in either upward, downward, or radial flow fashion with thelatter being preferred. In addition, the reactants may be in the liquidphase, a mixed liquid-vapor phase, or a vapor phase when they contactthe catalyst, with best results obtained in the vapor phase.

In the case where the trimetallic catalyst of the present invention isused in a reforming operation, the reforming system will comprise areforming zone containing a fixed bed or moving bed of the instanttrimetallic catalyst. This reforming zone may be one or more separatereactors with suitable heating means therebetween to compensate for theendothermic nature of the reactions that take place in each catalystbed. The hydrocarbon feed stream that is charged to this reformingsystem will comprise hydrocarbon fractions containing naphthenes andparaffins that boil within the gasoline range. The preferred chargestocks are those consisting essentially of naphthenes and paraffins,although in some cases aromatics and/or olefins may also be present.This preferred class includes straight run gasolines, natural gasolines,synthetic gasolines, and the like. On the other hand, it is frequentlyadvantageous to charge thermally or catalytically cracked gasolines orhigher boiling fractions thereof. Mixtures of straight run and crackedgasolines can also be used to advantage. The gasoline charge stock maybe a full boiling gasoline having an initial boiling point of from about50° F. to about 150° F. and an end boiling point within the range offrom about 325° F. to about 425° F., or may be a selected fractionthereof which generally will be a higher boiling fraction commonlyreferred to as a heavy naphtha--for example, a naphtha boiling in therange of C₇ to 400° F. In some cases, it is also advantageous to chargepure hydrocarbons or mixtures of hydrocarbons that have been extractedfrom hydrocarbon distillates--for example, straight-chainparaffins--which are to be converted to aromatics. It is preferred thatthese charge stocks be treated by conventional catalytic pretreatmentmethods such as hydrorefining, hydrotreating, hydrodesulfurization,etc., to remove substantially all sulfurous, nitrogenous, andwater-yielding contaminants therefrom and to saturate any olefins thatmay be contained therein.

In other hydrocarbon conversion embodiments, the charge stock will be ofthe conventional type customarily used for the particular kind ofhydrocarbon conversion being effected. For example, in a typicalisomerization embodiment the charge stock can be a paraffinic stock richin C₄ to C₈ normal paraffins, or a normal butane-rich stock, or ann-hexane-rich stock, or a mixture of xylene isomers, etc. In adehydrogenation embodiment, the charge stock can be any of the knowndehydrogenatable hydrocarbons such as an aliphatic compound containing 2to 30 carbon atoms per molecule, a C₄ to C₃₀ normal paraffin, a C₈ toC₁₂ alkylaromatic, a naphthene, and the like. In hydrocrackingembodiments, the charge stock will be typically a gas oil, heavy crackedcycle oil, etc. In addition, alkylaromatic and naphthenes can beconveniently isomerized by using the catalyst of the present invention.Likewise, pure hydrocarbons or substantially pure hydrocarbons can beconverted to more valuable products by using the trimetallic catalyst ofthe present invention in any of the hydrocarbon conversion processes,known to the art, that use a dual-function catalyst.

In a reforming embodiment, it is generally preferred to utilize thenovel trimetallic catalyst composite in a substantially water-freeenvironment. Essential to the achievement of this condition in thereforming zone is the control of the water level present in the chargestock and the hydrogen stream which is being charged. to the zone. Bestresults are ordinarily obtained when the total amount of water enteringthe conversion zone from any source is held to a level less than 50 ppm.and preferably less than 20 ppm.; expressed as weight of equivalentwater in the charge stock. In general, this can be accomplished bycareful control of the water present in the charge stock and in thehydrogen stream. The charge stock can be dried by using any suitabledrying means known to the art such as a conventional solid adsorbenthaving a high selecitivity for water; for instance, sodium or calciumcrystalline aluminosilicates, silica gel, activated alumina, molecularsieves, anhydrous calcium sulfate, high surface area sodium, and thelike adsorbents. Similarly, the water content of the charge stock may beadjusted by suitable stripping operations in a fractionation column orlike device. And in some cases, a combination of adsorbent drying anddistillation drying may be used advantageously to effect almost completeremoval of water from the charge stock. Preferably, the charge stock isdried to a level corresponding to less than 20 ppm. of H₂ O equivalent.In general, it is preferred to maintain the hydrogen stream entering thehydrocarbon conversion zone at a level of about 10 to about 20 vol. ppm.of water or less. In the case where the water content of the hydrogenstream is above this range, this can be conveniently accomplished bycontacting the hydrogen stream with a suitable desiccant such as thosementioned above at conventional drying conditions.

In the reforming embodiment, an effluent stream is withdrawn from thereforming zone and passed through a cooling means to a separation zone,typically maintained at about 25° to 150° F., wherein a hydrogen-richgas is separated from a high octane liquid product, commonly called an"unstabilized reformate". When a superdry operation is desired, at leasta portion of this hydrogen-rich gas is withdrawn from the separatingzone and passed through an adsorption zone containing an adsorbentselective for water. The resultant substantially water-free hydrogenstream can then be recycled through suitable compressing means back tothe reforming zone. The liquid phase from the separating zone istypically withdrawn and commonly treated in a fractionating system inorder to adjust the butane concentration, thereby controlling front endvolatility of the resulting reformate.

The conditions utilized in the numerous hydrocarbon conversionembodiments of the present invention are those customarily used in theart for the particular reaction, or combination of reactions, that is tobe effected. For instance, alkylaromatic and paraffin isomerizationconditions include: a temperature of about 32° F. to about 1000° F. andpreferably about 75° F. to about 600° F.; a pressure of atmospheric toabout 100 atmospheres; a hydrogen to hydrocarbon mole ratio of about0.5:1 to about 20:1 and a LHSV (calculated on the basis of equivalentliquid volume of the charge stock contacted with the catalyst per hourdivided by the volume of conversion zone containing catalyst) of about0.2 hr..sup.⁻¹ to 10 hr..sup.⁻¹. Dehydrogenation conditions include: atemperature of about 700 to about 1250° F., a pressure of about 0.1 toabout 10 atmospheres, a liquid hourly space velocity of about 1 to 40hr..sup.⁻¹ and a hydrogen to hydrocarbon mole ratio of about 1:1 to20:1. Likewise, typically hydrocracking conditions include: a pressureof about 500 psig. to about 3000 psig.; a temperature of about 400° F.to about 900° F.; a LHSV of about 0.1 hr..sup.⁻¹ to about 10 hr..sup.⁻¹; and hydrogen circulation rates of about 1000 to 10,000 SCF per barrelof charge.

In the reforming embodiment of the present invention the pressureutilized is selected from the range of about 0 psig. to about 1000psig., with the preferred pressure being about 50 psig. to about 600psig. Particularly good results are abtained at low pressure; namely, apressure of about 50 to 350 psig. In fact, it is a singular advantage ofthe present invention that it allows stable operation at lower pressurethan have heretofore been successfully utilized in so-called"continuous" reforming systems (i.e., reforming for periods of about 15to about 200 or more barrels of charge per pound of catalyst withoutregeneration) with all platinum monometallic catalysts. In other words,the trimetallic catalyst of the present invention allows the operationof a continuous reforming system to be conducted at low pressure (i.e.,100 to about 350 psig.) for about the same or better catalyst lifebefore regeneration as has been heretofore realized with conventionalmonometallic catalysts at higher pressure (i.e., 400 to 600 psig.). Onthe other hand, the stability feature of the present invention enablesreforming operation conducted at pressures of 400 to 600 psig. toachieve substantially increased catalyst life before regeneration.

Similarly, the temperature required for reforming is generally lowerthan that required for a similar reforming operation using a highquality catalyst of the prior art. This significant and desirablefeature of the present invention is a consequence of the selectivity ofthe trimetallic catalyst of the present invention for theoctane-upgrading reactions that are preferably induced in a typicalreforming operation. Hence the present invention requires a temperaturein the range of from about 800° F. to about 1100° F. and preferablyabout 900° F. to about 1050° F. As is well known to those skilled in thecontinuous reforming art, the initial selection of the temperaturewithin this broad range is made primarily as a function of the desiredoctane of the product reformate considering the characteristics of thecharge stock and of the catalyst. Ordinarily, the temperature then isthereafter slowly increased during the run to compensate for theinevitable deactivation that occurs to provide a constant octaneproduct. Therefore, it is a feature of the present invention that therate at which the temperature is increased in order to maintain aconstant octane product, is substantially lower for the catalyst of thepresent invention than for a high quality reforming catalyst which ismanufactured in exactly the same manner as the catalyst of the presentinvention except for the inclusion of the bismuth and rhodiumcomponents. Moreover, for the catalyst of the present invention, theC₅ + yield loss for a given temperature increase is substantially lowerthan for a high quality reforming catalyst of the prior art. Inaddition, hydrogen production is substantially higher.

The reforming embodiment of the present invention also typicallyutilizes sufficient hydrogen to provide an amount of about 1 to 20 molesof hydrogen per mole of hydrocarbon entering the reforming zone, withexcellent results being obtained when about 5 to about 10 moles ofhydrogen are used per mole of hydrocarbon. Likewise, the liquid hourlyspace velocity, (LHSV), used in reforming is selected from the range ofabout 0.1 to about 10 hr..sup.⁻¹, with a value in the range of about 1to about 5 hr..sup.⁻¹ being preferred. In fact, it is a feature of thepresent invention that it allows operations to be conducted at higherLHSV than normally can be stably achieved in a continuous reformingprocess with a high quality reforming catalyst of the prior art. Thislast feature is of immense economic significance because it allows acontinuous reforming process to operate at the same throughput levelwith less catalyst inventory than that heretofore used with conventionalreforming catalysts at no sacrifice in catalyst life beforeregeneration.

The following working examples are given to illustrate further thepreparation of the trimetallic catalytic composite of the presentinvention and the use thereof in the conversion of hydrocarbons. It isunderstood that the examples are intended to be illustrative rather thanrestrictive.

EXAMPLE I

This example demonstrates a particularly good method of preparing thetrimetallic catalytic composite of the present invention.

An alumina carrier material comprising 1/16 inch spheres is prepared by:forming an aluminum hydroxyl chloride sol by dissolving substantiallypure aluminum pellets in hydrochloric acid, addinghexamethylenetetramine to the resulting alumina sol, gelling theresulting solution by dropping it into an oil bath to form sphericalparticles of an aluminum-containing hydrogel, aging and washing theresulting particles, and finally drying and calcining the aged andwashed particles to form spherical particles of gamma-alumina containingabout 0.3 wt. % combined chloride. Additional details as to this methodof preparing the preferred gamma-alumina carrier material are given inthe teachings of U.S. Pat. No. 2,620,314.

An aqueous impregnation solution containing chloroplatinic acid, rhodiumtrichloride hydrate, bismuth trichloride, and hydrogen chloride is thenprepared. The alumina carrier material is thereafter admixed with theimpregnation solution. The amount of regents contained in thisimpregnation solution is calculated to result in a final compositecontaining, on an elemental basis, 0.375 wt. % platinum, 0.25 wt. %bismuth, and 0.25 wt. % rhodium. In order to insure uniform dispersionof the metallic components throughout the carrier material, the amountof hydrochloric acid used is about 3 wt. % of the alumina particles.This impregnation step is performed by adding the carrier materialparticles to the impregnation mixture with constant agitation. Inaddition, the volume of the solution is approximately the same as thevoid volume of the carrier material particles. The impregnation mixtureis maintained in contact with the carrier material particles for aperiod of about 1/2 hour at a temperature of about 70° F. Thereafter,the temperature of the impregnation mixture is raised to about 225° F.and the excess solution evaporated in a period of about 1 hour. Theresulting dried particles are then subjected to a calcination oroxidation treatment in an air atmosphere at a temperature of about 975°F. for about 1 hour. This oxidation step is designed to convertsubstantially all of the metallic ingredients to the corresponding oxideforms. The calcined spheres are then contacted with an air streamcontaining H₂ O and HCl in a mole ratio of about 30:1 for about 4 hoursat 975° F. in order to adjust the halogen content of the catalystparticles to a value of about 1 wt. %.

The resulting catalyst particles were analyzed and found to contain, onan elemental basis, about 0.375 wt. % platinum, about 0.25 wt. %rhodium, about 0.25 wt. % bismuth, and about 1 wt. % combined chloride.For this catalyst, the atomic ratio of rhodium to platinum is 1.26:1 andthe atomic ratio of bismuth to platinum is 0.622:1.

Thereafter, the catalyst particles are subjected to a dry reductionstep, designed to reduce the platinum, rhodium, and bismuth componentsto the corresponding elemental metallic states by contacting them for 1hour with a substantially pure hydrogen stream containing less than 5vol. ppm. H₂ O at a temperature of about 1050° F., a pressure slightlyabove atmospheric, and a flow rate of the hydrogen stream through thecatalyst particles corresponding to a gas hourly space velocity of about720 hr..sup.⁻¹.

EXAMPLE II

A portion of the Example trimetallic catalyst particles produced by themethod described in Examplle I are loaded into a scale model of acontinuous, fixed bed reforming plant of conventional design. In thisplant, a heavy Kuwait naphtha and hydrogen are continuously contacted atreforming conditions: a liquid hourly space velocity of 1.5 hr..sup.⁻¹ ;a pressure of 100 psig.; a hydrogen to hydrocarbon mole ratio of 5:1,and a temperature sufficient to continuously produce a C₅ + reformate of102 F-1 clear. It is to be noted that these are exceptionally severeconditions.

The heavy Kuwait naphtha has a API gravity at 60° F. of 60.4, an initialboiling point of 184° F., a 50% boiling point of 256° F., and an endboiling point of 360° F. In addition, it contains about 8 vol. %aromatics, 71 vol. % paraffins 21 vol. % naphthenes, 0.5 wt. % parts permillion sulfur, and 5 to 8 wt. parts per million water. The F-1 clearoctane number of the raw stock is 40.0.

The fixed bed reforming plant is made up of a reactor containing thetrimetallic catalyst, a hydrogen separation zone, a debutanizer column,and suitable heating, pumping, cooling, and controlling means. In thisplant, a hydrogen recycle stream and the charge stock are commingled andheated to the desired temperature. The resultant mixture is then passeddownflow into a reactor containing the trimetallic catalyst as a fixedbed. An effluent stream is then withdrawn from the bottom of thereactor, cooled to about 55° F. and passed to a separating zone whereina hydrogen-rich gaseous phase separates from a liquid hydrocarbon phase.A portion of the gaseous phase is continuously passed through a highsurface area sodium scrubber and the resulting water-free hydrogenstream recycled to the reactor in order to supply hydrogen thereto andthe excess hydrogen over that needed for plant pressure is recovered asexcess separator gas. The liquid hydrocarbon phase from the hydrogenseparating zone is withdrawn therefrom and passed to a debutanizercolumn of conventional design wherein light ends are taken overhead asdebutanizer gas and C₅ + reformate stream recovered as bottoms.

The test run is continued for a catalyst life of about 20 barrels ofcharge per pound of catalyst utilized, and it is determined that theactivity, selectivity, and stability of the present trimetallic catalystare vastly superior to those observed in a similar type test with aconventional commercial reforming catalyst. More specifically, theresults obtained from the subject catalyst are superior to the platinummetal-containing catalyst of the prior art in the areas of hydrogenproduction, C₅ + yield at octane, average rate of temperature increasenecessary to maintain octane, and C₅ + yield decline rate.

It is intended to cover by the following claims all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in the catalystformulation art of the hydrocarbon conversion art.

I claim as my invention:
 1. A process for converting hydrocarbon whichcomprises contacting the hydrocarbon, at hydrocarbon conversionconditions, with a catalytic composite consisting essentially of porouscarrier material containing, on an elemental basis, about 0.01 to about2 wt. % platinum or palladium, about 0.01 to about 2 wt. % rhodium,about 0.1 to about 3.5 wt. % halogen, and bismuth in an amountsufficient to result into an atomic ratio to bismuth of platinum orpalladium of about 0.1:1 to about 1:1, wherein the platinum orpalladium, rhodium, and bismuth are uniformly dispersed throughout theporous carrier material and wherein substantially all of the platinum orpalladium, rhodium, and bismuth are present in the correspondingelemental metallic states.
 2. A process as defined in claim 1 whereinthe porous carrier material is a refractory inorganic oxide.
 3. Aprocess as defined in claim 2 wherein the refractory inorganic oxide isalumina.
 4. A process as defined in claim 1 wherein the halogen iscombined chloride.
 5. A process as defined in claim 1 wherein the atomicratio of bismuth to platinum or palladium contained in the composite isabout 0.1:1 to about 0.75:1.
 6. A process as defined in claim 1 whereinthe atomic ratio of rhodium to platinum or palladium in the composite isabout 0.1:1 to about 2:1.
 7. A process defined in claim 1 wherein thecatalytic composite contains about 0.01 to about 0.5 wt. % sulfur,calculated on an elemental basis.
 8. A process as defined in claim 1wherein the catalytic composite contains about 0.05 to about 1 wt. %platinum, about 0.5 to about 1 wt. % rhodium, about 0.5 to about 1.5 wt.% halogen, and an atomic ratio of bismuth to platinum of about 0.1:1 toabout 0.75:1.
 9. A process as defined in claim 1 wherein the contactingof the hydrocarbon with the catalytic composite is performed in thepresence of hydrogen.
 10. A process as defined in claim 1 wherein thetype of hydrocarbon conversion is catalytic reforming of a gasolinefraction to produce a high octane reformate, wherein the hydrocarbon iscontained in the gasoline fraction, wherein the contacting is performedin the presence of hydrogen, and wherein the hydrocarbon conversionconditions are reforming conditions.
 11. A process as defined in claim10 wherein the reforming conditions include a temperature of about 800to about 1100° F., a pressure of about 1 to about 1000 psig., a liquidhourly space velocity of about 0.1 to about 10 hr..sup.⁻¹, and a moleratio of hydrogen to hydrocarbon of about 1:1 to 20:1.
 12. A process asdefined in claim 10 wherein the contacting step is performed in asubstantially water-free environment.
 13. A process as defined in claim10 wherein the reforming conditions include a pressure of about 50 to350 psig.
 14. A catalytic composite consisting essentially of a porouscarrier material containing, on an elemental basis, about 0.01 to about2 wt. % platinum or palladium, about 0.01 to about 2 wt. % rhodium,about 0.1 to about 3.5 wt. % halogen, and bismuth in an amountsufficient to result in an atomic ratio of bismuth to platinum orpalladium of about 0.1:1 to about 1:1, wherein the platinum orpalladium, rhodium, and bismuth are uniformly dispersed throughout thecarrier material and wherein substantially all of the platinum orpalladium, rhodium, and bismuth are present in the correspondingelemental metallic states.